Not at all. If anything is too slow, it is the AMD CPU.
The Quadro K620 could be too slow for some Photoshop workflows. The memory bandwidth, which does impact 2D work, is the slowest of the whole Quadro desktop family at 29 GPps. If you are simply working with static photos, this may not be a bottleneck. However, if you are doing lots of culling (using Bridge or Lightroom to go quickly through lots of high-res photos like in sports photography), then you would definitely notice better performance with a faster card. The K2200 would probably be able to keep up with the rest of your system at 80 GBps. Note also that the really high memory bandwidth cards (i.e. K6000 with 288 GBps) are faster still, but again for Photoshop work anything over 100GBps would probably not "feel" any faster.
Here's some more info on AMD Processor.
AMD FX(tm)-6100 Six Core
16 GB RAM
64 bit Operating System
Any suggestions for improvement will be greatly appreciated.
Thank you in advance for your consideration.